Sol-gel synthesis of nanostructured perovskite-like gadolinium ferrites

Nanodispersed layered perovskite-like ferrites GdSrFeO₄ and Gd₂SrFe₂O₇ have been synthesized for the first time in accordance with the sol-gel technology using the citrate-nitrate technique. The citratenitrate and glycine-nitrate techniques of the synthesis of a complex oxide GdFeO₃ with a three-dimensional perovskite structure have been optimized. The decrease of the ferrite particle size from 10 μm in the case of the solid-phase high-temperature synthesis to 50–200 nm in the case of the sol-gel technology has been demonstrated.     

Infrared and Raman spectral studies in cement and concrete (review)

Applications of infrared and Raman spectroscopy in the field of cement and concrete as reported over the years are quite significant. Specific applications in areas such as, identification of cement phases including different polymorphic and crystal forms, estimation of phases in cement, cement hydration, admixture, concrete-polymer, alkali-aggregate reactions, etc, have been recognised with various degree of success. More application of these techniques is envisaged with further advancement in instrumentation and in sample preparation, especially in newer products where organic substances play dominant role.     

Infrared studies of ethene hydrogenation over ZrO2

Hydrogenation of adsorbed ethene over ZrO₂ at low temperature was observed by in situ infrared transmission spectroscopy. It was found that di-hydrogen was directly activated on the site where ethene was already adsorbed, which was confirmed by the comparison of adsorbed species produced during the reaction and adsorbed ethane species.     

十二烷基磺酸根插层Ni~(2+)-Fe~(3+)/Co~(2+)-Ni~(2+)-Fe~(3+) LDHs及其结构研究

应用水热技术制备了二元Ni2+-Fe3+-CO23- LDHs和三元Co2+-Ni2+-Fe3+-CO32- LDHs,以十二烷基磺酸根离子作为插层客体,通过离子交换反应在酸性溶液中实现了十二烷基磺酸根插层Ni2+-Fe3+ LDHs和Co2+-Ni2+-Fe3+-LDHs。十二烷基磺酸根在Ni2+-Fe3+LDHs层间出现了2种空间导向和排列:即十二烷基磺酸根以单层垂直方向排布和以双层垂直方向排布在层间;十二烷基磺酸根在三元组分Co2+-Ni2+-Fe3+-LDHs层间只有一种空间排列方式,即十二烷基磺酸根以单层垂直方向排布于Co2+-Ni2+-Fe3+-LDHs层间。     

Co2+-Ni2+-Fe3+-CO2-3LDHs的水热合成及表征

以尿素作为沉淀剂,酒石酸钠作为络合剂,氮气作为保护气,借助于水热合成技术成功合成了高结晶性规则形貌三元组分Co<'2+>-Ni<'2+>-Fe3<'3+>-CO<'2-><,3>-LDHs,通过XRD、SEM、FTIR、EDS、原子吸收等分析手段对合成产物进行了表征.     

Co2+ Ion Exchange in Zeolite NaA

Abstract

⁶⁰Co²⁺ ion exchange at room temperature (20°C) from aqueous cobalt chloride solution with zeolite NaA either hydrated or heated at 150 and 600°C has been studied. In all samples a fast Co²⁺ uptake is found in which 2 meq Na⁺ ions/g of zeolite are replaced by cobalt ions. This process is stable and no desorption is observed. These results are quite different from those obtained in previous work with zeolite NaY which showed that sorption was followed by a desorption process.     

Effects of Co2+ on the erythromycin biosynthesis

Erythromycin biosynthesis is a highly complicated process, which involves both primary metabolism and secondary metabolism. The specific activities of the key enzymes related to glucose metabolism such as hexose kinase (HK), glucose-6-phosphate dehydrogenase (6-PDH), phosphofructokinase (PFK), and isocitrate dehydrogenase (ICD), were determined in Saccharopolyspora erythraea. The specific activities of the enzymes involved in secondary metabolism, such as methylmalonyl-coenzyme A mutase (MCM) and methylmalonyl-coenzyme A transcarboxylase (MCT), were detected as well. Some organic acids contained in fermentation broth were also analyzed. The results show that Co²⁺ is able to increase erythromycin biosynthesis. It maybe due to Co²⁺ improving the specific activities of methylmalonyl-coenzyme A mutase and methylmalonyl-coenzyme A transcarboxylase. Meanwhile, it also enhances the flux of the glucose metabolism pathway. Translated from Journal of East China University of Science and Technology (Natural Science Edition), 2006, 32(11): 1 280–1 284 [译自: 华东理工大学学报 (自然科学版)]     

Novel combustion synthesis of La3+-substituted MnFe2O4

La³⁺-substituted MnFe₂O₄ compounds have been prepared by using a novel combustion synthesis method. This process was found to yield homogeneous, finely crystalline powders without intermediate decomposition and/or calcination steps. Combustion-synthesized powders were sintered at 1000°C, and structural features of thus prepared materials were characterized by XRD analysis and FT-IR spectroscopy. The dc electrical conductivity of synthesized materials has been measured as a function of temperature up to 1000°C. The materials have shown semiconducting behavior at elevated temperatures. The ac electrical conductivity of synthesized samples was found to increase with increasing applied frequency. The dielectric constant and dielectric loss tangent have also been characterized. The article is published in the original.     

KINETICS AND MECHANISM OF ISOTOPIC EXCHANGE FOR Co2+/Co Co2+ IN TIN(IV) ANTIMONATE

ABSTRACT

The rate of the isotopic exchange of cobalt ion between tin(IV) antimonate ion exchanger in the Co Co²⁺ form and aqueous solutions vas determined radiometrically. Self-diffusion coefficients for cobalt ion were measured as a function of the variable capacity for that ion in solutions of varying acidity. The effect of a heat treatment on the rate of the isotopic exchange reaction in tin(IV) antimonate vas also studied. The rate vas controlled by the particle diffusion of cobalt ion and increased by heating temperature and decreased with increase of ion exchange capacity. Values for the diffusion coefficentst activation energy and entropy of activation have been evaluated which give some information regarding the mechanism of ion exchange on the surface of inorganic materials.     

滤波程序对标准Co2+、Ni2+、Zn2+体系的定量分析

利用编写的滤波解析程序,对极谱分析、分光光度分析以及色谱分析中互为干扰组分进行同时测定.其主要特色就是把卡尔曼滤波和超定方程组结合起来,以标准物数据输入时,程序能自动判断出最佳路径,从而确定试样数据的入口,并直接计算出样品中各组分的含量.对解析一般性重叠和严重重叠(甚至完全重叠)的测试峰,效果非常好.在伏安分析中对Co2 、Ni2 、Zn2 体系进行定量分析,回收率在97.6%～104.1%之间,相对标准偏差(RSD)为1.29%～2.86%(n=5).方法可准确进行定量检测,能排除其他成分干扰,重现性好.     

Co~(2+)-TiO_2纳米粒子的制备及光催化性能研究

用溶胶-凝胶法制备Co2+-TiO2纳米粒子,利用X-射线衍射(XRD)、透射电子显微镜(TEM)和紫外-可见光谱(UV-vis)对样品进行表征。以对-硝基苯酚为目标降解物,考察了Co2+掺杂对纳米TiO2光催化活性的影响。结果表明,适量Co2+掺杂抑制了纳米TiO2晶粒的成长,使TiO2的光谱响应范围向可见光拓展,有利于提高TiO2的光催化活性,提高TiO2对太阳光的利用率;Co2+-TiO2能有效提高对-硝基苯酚的光催化降解,掺Co量(以摩尔计)不同的TiO2光催化活性依次为:0.5%>0.25%>0%>5%>10%。     

分光光度法同时测定镀液中钴和镍

研究了在pH为8.0的氯化铵-氨水缓冲溶液中,以4-(2-吡啶偶氮)-间苯二酚为显色剂,应用双波长K系数分光光度法同时测定镀液中的钴和镍。钴以512 nm/482 nm为波长对,其线性范围为0.080~1.0μg/mL;镍以496 nm/526 nm为波长对,其线性范围为0.040~1.0μg/mL。此法用于合金镀液中钴和镍的同时测定,取得了较满意的结果。     

微波辐射作用下La3+,Co2+,Cu2+和Zn2+与Y沸石的离子交换

采用微波辐射法制备了La^3＋/Y、Co^2＋/Y、Cu^2＋/Y和Zn^2＋/Y离子交换型沸石催化剂。通过考察交换原液浓度、加热时间、微波功率等因素对交换度的影响,得出交换反应的适宜工艺条件为：交换原液浓度0.12 mol·L^-1（La^3＋）、0.06 mol·L^-1（Co^2＋）、0.08 mol·L^-1（Cu^2＋）和0.10 mol·L^-1（Zn^2＋）,加热时间6 min（Co^2＋和Zn^2＋）、12 min（La^3＋和Cu^2＋）,微波辐射功率520 W（La^3＋,Co^2＋,Cu^2＋和Zn^2＋）。La^3＋,Co^2＋,Cu^2＋和Zn^2＋与Y沸石的一次交换度分别为80.8%（La^3＋）、69.6%（Zn^2＋）、67.5%（Cu^2＋）和63.8%（Co^2＋）。对比实验结果表明,在相同工艺条件下,微波辐射加热法所需时间仅为传统加热法的1/40～1/80。XRD结果表明,微波辐射对沸石晶体结构无破坏作用。采用“二交二焙”法可使La^3＋与Y沸石的交换度由80.8%提高到91.6%。     

Kinetics of Exchange of Cs+, Co2+ and Sr2+ on Synthetic Hydrous Titanium Oxides

Abstract

In the present work, a study of the kinetics of adsorption of Cs⁺, Co²⁺, and Sr²⁺ on four hydrous titanium oxides, prepared in different media, and designated as Ti‐I, Ti‐II, Ti‐III, and Ti‐IV, was carried out. In the aqueous medium, the internal diffusion coefficients, D_i for Cs⁺ were found to be equal to 3.7×10^?9, 3.7×10^?9, 2.3×10^?9, and 1.5?10^?9 cm²/s, in Ti‐I, Ti‐II, Ti‐III, and Ti‐IV, respectively. For Co²⁺ and Sr²⁺, these values are equal to 0.96×10^?9 and 0.64×10^?9 cm²/s, respectively for Ti‐IV. In Ti‐IV, D_i for all ions generally increases on adding methanol or propanol. This is probably due to greater dehydration, leading to faster ion diffusion, and, hence, to a decrease of ion mobility due to stronger interaction with the surface. In all media in Ti‐IV, the order: D_i(Cs⁺)>D_i(Co²⁺)≥D_i(Sr²⁺) was found which is due to a stronger interaction of the bivalent ions with the exchange sites.     

The effect of Co2+, Cu2+, Fe2+ and Fe3+ during electrowinning of nickel

The effects of the impurities Co²⁺, Cu²⁺, Fe²⁺, Fe³⁺ on the current efficiency, physical appearance, purity, crystallographic orientation and surface morphology of the deposit and on nickel deposition polarization behaviour during nickel electrowinning were determined. The current efficiency did not change significantly in the presence of these impurities over the concentration range studied, but certain changes in the purity and physical appearance of the deposit were observed. Based on the physical appearance of the electrodeposited nickel, the tolerance limits of the impurities in the electrolyte are reported. The tolerance limit of Co²⁺ was a maximum at 500 p.p.m. and a minimum at 5 p.p.m. in the case of Fe²⁺. No deviation of nickel structure from fcc was observed in the presence of any of these impurities but the peak height values for different orientations showed variations with all the impurities and the values also changed with increase in the impurity concentrations. The surface morphology of electrodeposited nickel also changed in the presence of the impurities. The potentiodynamic scan curves for electrodeposition of nickel showed deviations in the presence of all the impurities except Cu²⁺. Based on the results, an attempt is made to correlate the effects of the various factors investigated.     

Local Ordering Around Tetrahedral Co2+ in Silicate Glasses

Alkali lime silicate glasses containing 5 wt% of CoO were investigated by Co K‐edge XANES and EXAFS and optical absorption spectroscopy. Our results reveal the presence of tetrahedral Co²⁺ connected with the glass network, with a ^IVCo–O–Si angle of 134°. Changing the alkali from K⁺ to Na⁺ induces an increase of the local disorder around Co²⁺, as shown by a decrease of the contribution from the second neighbors in the EXAFS signal. We propose two models for interpreting the structure of the second shell of neighbors. Our results provide a structural basis for rationalizing the optical properties of Co²⁺ species in glasses.     

Ionic migration and charge reduction in Ni2+-, Co2+- and Zn2+-exchanged Texas montmorillonite

Controlled calcination of ion-exchanged Texas montmorillonite leads to layer charge reduction. Detailed chemical analyses of both exchangeable and unexchangeable metal species lead to the conclusion that, in complete contrast to the situation with Wyoming bentonite, Ni²⁺, Co²⁺ and Zn²⁺ are all capable of migrating from the interlamellar space into the octahedral region of the sheets where they are (i) isomorphously exchanged for Mg²⁺, and to a proportionately smaller extent, for Fe²⁺, (ii) trapped in the octahedral vacancies. In addition, they are converted to unexchangeable species on the interlamellar sheet surfaces by high temperature hydrolysis leading to hydroxide or oxide formation. It is suggested that protons within the octahedral region are bound as -OH⁺ ₂rather than simply physically trapped.     

一种新型Co~(2+)荧光探针的合成及其性能研究

以8-羟基喹啉衍生物与2,4-二羟基苯甲醛为原料,合成了一种新型的离子荧光探针HQHD。该化合物结构通过红外、氢谱、碳谱以及高分辨质谱进行确认。当以V(乙腈)∶V(水)=1∶9缓冲溶液为溶剂时,荧光探针的性能研究表明,在16种常见金属离子和NH~+_4中,HQHD对Co~(2+)具有较好的专一识别能力,p H在6.98~8.6范围内对Co~(2+)的识别能力最强。当Co~(2+)与其他离子形成共存离子溶液时,并不影响HQHD对Co~(2+)的检测效果,说明配体HQHD具有较强的抗干扰能力。当Co~(2+)在0.5×10~(-5)~5×10~(-5)mol/L的浓度范围内,体系的荧光强度ΔF与Co~(2+)的浓度呈现良好的线性关系,线性拟合系数为0.982 6,检测限为9.77×10~(-8)mol/L。Job's plot曲线表明,Co~(2+)与配体比为1∶1。     

光度法同时测定合金镀液中Co2+与Ni2+

提出采用双波长分光光度法同时测定镍钴合金镀液中Co2 与N i2 的含量。通过筛选确定PAR乙醇液作为显色剂。测得Co2 与N i2 的最大吸收波长分别为510 nm,490 nm,以此作为测定波长。该法的测量范围为30~1 200μg/LCo2 ,25~1 000μg/L N i2 。讨论了显色剂用量、酸度及显色时间对吸光度的影响,从而确定了显色条件。对4种镍-钴合金镀液进行加标回收实验的结果表明,该法精确度高,回收率达到99.7%,操作简单,实用性强。